Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quando a escola de Logan Township, Pensilvânia, se juntou à Conferência?
 ###Tabelas: CREATE TABLE honey-producing_and_consuming_countries (honey-producing_and_consuming_countries_id AUTO_INCREMENT PRIMARY KEY, Rank VARCHAR, Country VARCHAR, 2009 VARCHAR, 2010 VARCHAR, 2011 VARCHAR) CREATE TABLE goals_for_senior_national_team (goals_for_senior_national_team_id AUTO_INCREMENT PRIMARY KEY, Date VARCHAR, Venue VARCHAR, Score VARCHAR, Result VARCHAR, Competition VARCHAR) CREATE TABLE post_season (post_season_id AUTO_INCREMENT PRIMARY KEY, Year VARCHAR, Team VARCHAR, Comp VARCHAR, Long VARCHAR, Rate VARCHAR, RAtt VARCHAR, RYds VARCHAR, RAvg VARCHAR, Lost VARCHAR) CREATE TABLE current_members (current_members_id AUTO_INCREMENT PRIMARY KEY, Institution VARCHAR, Location VARCHAR, Nickname VARCHAR, Founded INT, Type VARCHAR, Enrollment INT, Joined INT) CREATE TABLE list_of_special_representatives (list_of_special_representatives_id AUTO_INCREMENT PRIMARY KEY, Name VARCHAR, Born-Died VARCHAR, Took Office VARCHAR, Left Office VARCHAR, Country VARCHAR)  
SELECT Joined FROM current_members WHERE Location = Logan Township, Pennsylvania